Mechanically-self-excited piezo-electric stabilizing modulator



March 193!- A. MCL. NICOLSON IECHNICALLY SELF EXCITED PIEZO ELECTRIC STABILIZING IODULATOR Filed Jan. 18. 1927 Fig. 1

POWER AMPLIFIER INVENTOR ALEXANDER McLEAN NICOLSON ATTORNEY Patented Mar. 10, 1931 barren STATES PATENT OFFICE ALEXANDER MCLEAN NIGOLSON, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGN- MENTS, TO FEDERAL TELEGRAPH COMPANY, A CORPORATION OF CALIFORNIA MECHANICALLY-SELF-EXCITED PIEZO-ELECTRIC STABILIZING MODULATOR Application filed January 18, 1927. Serial No. 161,854.

such apparatus utilizin piezo-electric crystal devices for the stabilization and control of the high frequency oscillations and for the production of low frequency oscillations corresponding to the'signals to be transmitted.

It is an object of this invention to provide a method and apparatus for mechanically exciting a piezo-electric crystal device at the relatively high frequencies utilized for car- 23 rier currents and radio currents'to cause generation of electrical oscillations which may be modulated and impressed upon a load circuit. o

It is a further object of this invention to p id a method and apparatus for mechanically vibrating or stressing a piezo-electric crystal device at the frequency desired for such transmission, and also, in accordance with acoustic signals which it is desired to o transmit as modulations of the high fre- V quency'signalling oscillations.

It is still a further object of this invention to provide an apparatus for mechanically vibrating or stressing a piezo-electric crystal i device in a manner to produce high frequency signalling oscillations modulated in accordance with lower frequency signals.

It is still a further object of this invention to provide an apparatus of the class de- 49 scribed, the natural frequency of which may .43 The features of novelty which I believe to be controlled without altering'the physical characteristics of the piezoelectric crystals or crystal devices. Still other objects will be apparent from the specification.

be characteristic of my invention are set forth with particularity in the appended claims. Myinvention itself, however, both as to its underlying principles and as to its particular embodiments will best be understood by reference to the specification and accompanying drawing, in which:

Fig. 1 illustrates diagrammatically apparatus in accordance with one form of my invention.

Fig. 2 illustrates apparatus according to a different form thereof.

In accordance with my invention, I utilize a piezo-electric crystal device provided with electrodes arranged thereon to withdraw charges generated thereupon by vibration of the crystal device, and I preferably arrange this crystal device in such manner that it will be positively vibrated or stressed by a mechanical connection in accordance with and at the frequency of the high frequency oscilchanically vibrating the crystal device simultaneously at and in accordance with the frequencyof signals desired to be transmitted: for example in accordance with the frequencies of speech, music, and the like.

The vibrations corresponding to speech, music, and the like may be introduced by a separate mechanical vibrating means, or may be impressed upon the crystal device by the same mechanical connection which drives it at the high frequency desired.

I may also provide mechanical tuning means for altering or controlling the natural frequency of the system within limits: for example, masses may be provided with arrangements for varying their position for the purpose of varying the constants of the mechanical vibrating system, and thereby varying its natural frequency. 7

I may also provide an acoustic device such for example as a cone adapted to be vibrated by the signals desired to be transmitted such as speech, music and the like. The cone may be secured to one of the crystal devices to vibrate the same in accordance with speech, and thereby produce electrical oscillations corresponding thereto, or in some instances, it may be used to operate an ordinary microphone of the coventional type, the output from which may be amplified, if desired, and imand thereby converted into mechanical vibrations which are impressed upon the crystal device which is stressed at high frequency, giving rise to the high frequency oscillations.

The crystal system is preferably associated with the input and output circuit of an amplitying system, such as a thermionic amplifier in such manner as to be self-exciting to produce high frequency oscillations modulated according to the desired signal, the output of which, maybe amplified tothe extentdesired and impressed upon a load circuit, such for example as a wire line or an antenna.

' Referring now more particularly to Fig." '1 in which I have shown one form of my invention, 1 designates a piezoelectric crystaldevice providedwith electrodes 2 and 3, and

if desired, with mounting plates A and 5, the

crystal device being so chosen'and arranged that its natural frequency otvibration corresponds to the high frequency oscillations desiredto be produced. A second crystal device may be provided having electrodes 7 and 8, and also if desired, end plates 9 and'lO. A suitable acoustic device such as cone 7,-11

maybe secured to the crystal device 6 in such manner as to cause vibration thereof in re sponse to the vibration of the cone 11: also, a

mechanical connection 12 will be provided between crystaldevice 1" and crystal device 6 for the purpose "of communicatingthe vibrationsof the former to the latter. A suitable 'amplifyingsystem comprising as many stages as may be desired'will beprovided herein diagrammatically shown as alsingle thermionic amplifier 13,- provi'dedwith a control elec trodeor grid li an anode 15, and a cathode '16. -The output circuit of the amplifier comprisesecoil 17-and a source of potential such as battery 19, and a condenser 18 in shuntth'erewith. Electrodes 3 and 7; are connectedtogether and to the filament system. Electrode 8,may be connected to the grid 14, whereas electrode 2 is connected to suitable intermediate pointion coil 17. A second coil 27 may be inductively or otherwise associated with coil 17 to supply the modulated high frequency currents to a suitablepower amplifier, the output 'of which may be impressed upon a load circuitsuch as an antenna 25 through the medium of coils 23 and .24. I

In the operation ofthe-sy'stem. shown, the intermediate point on coil 17will be so select ed that a suitable amount of energy from the output circuitis impressed upon the crystal device 1 through the medium of electrodes 2 and 3,causing said device to vibrate at its natural frequency and thereby through mechanical connection 12 impressing these vibra tions upon the crystal device 6. The forcible vibration or stressing of the crystal device 6 causes the production of oscillations corresponding thereto upon the electrodes 7 and 8 I controlling the input circuitof amplifier 13;

ltzwill be seen, therefore,ithat proper adj ust-; .ment willcause the generation of sustained oscillations of the frequency desired, which oscillations may be amplified to the extent desired. and impressed upon the load circuit. It now a sound wave strikes upon the cone 11, the crystal device 6 in addition to its high frequency vibrations will have vibrations of a relatively lower range superimposed thereupon, which will cause the production of electrical oscillations corresponding to the sound superimposed upon the high frequency'oscillations, theefiect of which through the operation of the amplifier 13, is to produce high frequency oscillations in the output circuit of said amplifier modulated ata frequency corresponding to the speech.

For the purpose of conserving energy and for other reasons, it is desirable 'to maintain the mass of the mechanical connection 12 and the mass of the crystal device 6, forming the load upon crystal device-1, as small as possible consistent with the necessary strength 1 to secure reliable operation, as otherwisedifiiculties will be encountered in the use of high powerin the amplifier,- dissipation of energy in the mechanical coupling, production of parasitic resonances, and the like. 7

Under certain conditions, I may prefer to utilize the arrangementj shown in Fig. 2,

. wherein 3O designates a piezo-electric crystal device provided with suitable electrodes 31 and 32 connected in the input circuit of the amplifier 13 and shunted if desired, by

means of a variable inductance 28, alsoif desired, variable condenser 29 for electrical tuning. A second piezoelectric crystal device 33 is provided having electrodes 34 and .35 associated therewith, and in addition, a

third crystal device 36 having an electrode 37 A mechanical connection 88 is provided betweencrystal device 30 and crystal device 7 36, and a second mechanical, connection 39 through variable condenser 50 to the other 7 end of said coil, permitting the desired adjustment of the amount-of energy impress-ed upon the crystal device33. The operation of this form of my invention may now be un derstood.

7 If 'a suitable amount of energy be 1111 pressed uponcrystal 33, vibrations will' be transmitted through the mechanical coupling between crystal device 36' and crystal device .33 which connection may be in the form of means 39 to and through crystal device 36, to and through the mechanical coupling means 38 to the crystal device 30. Vibration of said device will cause the generation of corresponding electrical oscillations which are impressed across the input circuit of amplifier 13, which may be tuned to the desired carrier frequency by means of coil 28 and condenser 29. The natural frequency of the composite mechanical and piezoelectric device is subject to control by the mechanical tuning means attached to the link 38 and by the mechanical tuning means attached to of the high frequency desired for radio or carrier current signalling, or lower frequencies if desired.

Relatively lower frequencies maybe caused to appear as modulations of the high frequency signalling oscillations by causing the system to vibrate, also at the low frequencies desired. This may be done, for example, by

" impressing upon the intermediate crystal 36 electrical oscillations corresponding to speech or music which may be picked up by cone l1, and impressed upon crystal device 6, causing the production of electrical oscillations which are impressed upon crystal 36 by means of a connection between electrode 8 and electrode 37 on the one hand, and between electrode 7 and end plate 39 on the other hand.

This, as will be understood, will cause mechanical vibrations of the crystal device 86, which vibrations, as well as the high frequency vibrations, will be transmitted to the crystal device 30 through the medium of the link 38. Under these conditions, the high frequency oscillations flowing in the output circuit of amplifier 13. will. be modulated in accordance with the vibrations picked up by the cone 11.

The modulated high frequency currents as will be understood, may be amplified to the diagrammatically shown may comprise de vices of any material, size shape and arrangement known in the art and suitable for the purpose, and may for example comprise arrangements described and 'claimec in my copending applications entitled Cast piezo-electric device, Serial No. 155,897, filed Dec. 20, 1926; Composite piezo-electric crystal device, Serial No. 155,898, filed Dec. 20, 1926; Composite piezo-electric torsion device, Serial No. 155,899, filed Dec. 20, 1926; Composite piezo-electric acoustic device, Serial No. 160,358, filed Jan. 11, 1927; Internally clamped composite piezo-electric torsion device, Serial No. 155,900, filed Dec. 20, 1926; Internally clamped composite piezo-electric acoustic device, Serial No. 160,- 359, filed Jan. 11, 1927; and Orientation of component crystals in composite piezoelectric devices, Serial No. 155,902, filed Dec. 20, 1926.

While I have shown and described certain preferred forms of my invention, it will be understood that modifications and changes may be made without departing from the spirit and scope of my invention, as will be understood by those skilled in the art.

I claim:

1. In a system for producing electrical oscillations of relatively high frequency, modulated at a range of relatively lower frequencies, a thermionic amplifier, input and output circuits associated therewith, a piezoelectric crystal device connected in said input circuit, said crystal device converting mechanical vibrations thereof into electrical oscillations, and mechanical means connected with said crystal device for vibrating said crystal device at the frequency of oscillations desired to be produced and at the frequencly desired to modulate said oscillations.

2. n a system for producing electrical oscillations of relatively high frequency, modulated at a range of relatively lower frequencies, a thermionic amplifier, input and output circuits associated therewith, a piezoelectric crystal device connected in said input circuit, said crystal device being so chosen and arranged as to convert mechanical vibrations thereof into electrical oscillations, and mechanical means for. vibrating said crystal device at the frequency of oscillations desired to be produced and at the frequency desired to modulate said oscillations, said means comprising a piezo-electric crystal device having a natural frequency corresponding to the frequency of oscillations to be produced and a link of piezo-electrically inactive material interconnecting said piezoelectric crystal devices.

3. In a system for producing electrical oscillations of relatively high frequency, modulated at a range of relatively lower frequencies, a thermionic amplifier, input and output circuits associated therewith, a piezoelectric crystal device connected in said input circuit, said crystal device being so chosen and arranged as to convert mechanical vibrations thereof into electrical oscillations, and mechanical means for vibrating said crystal device at the frequency of oscillations v. desired to be produced, and at the frequency desired to modulate said oscillations, said means comprising a plezo-electric crystal ole- I 5 output circuits associated therewith, a piezoelectric crystal device connected in said input circuit, said crystal devicebeing so chosen and arranged as to convert mechanical vibrations thereof into electrical oscillations, and mechanical means for vibrating said'crystal device at the frequency of oscillations desired to be produced and at the frequency desired to :modulate said oscillations, said means comprisinga piezo-electric crystal device having a natural frequency corresponding to the frequency of oscillations to be produced, and connected in the output circuit of saidamplifier and a link of piezo-electrically inactive material interconnecting said piezoelectric crystal devices.

' In a system for producing-electrical oscillations of relatively high frequency, modulated at a range of relatively lower freoutput circuits connected therewith, a pluraL ity of pieZo-electric crystal devices, one of said crystal devices being connected in said input circuit, another of said crystal devices being connected in saidvoutput circuit, a mechanical connection formed by a link of piezoelectrically inactive material extending between said crystal devices, said mechanical connection being so chosen and arranged that the natural frequency of the system corresired, and means for causing said mechanical I connection tovibrate in accordance with signals desired to modulate said high frequency oscillations. I r Y O 6. In a systemfor producing electrical os- -'c llat1ons of relativelyhigh frequency, modulated at a range of relatively lower -frequen-- cies, a thermionic amplifier, input and output circuits connected therewith, a'plurality of piezo-electric crystal devices, one of said crystal devices being connected in said input circuit, another of said crystal devices being connected in said output circuit, a

mechanical connection formed by a link of piezo-electrically inactive material extend-i ing between said crystal devices, said mef -chanic'al connection being so chosen and arranged that-the' natural frequency of the system corresponds tothe frequencyof oscil- .lations desired, and means for causing said quencies, a thermionic amplifier, input and spondsto the frequency of oscillations demechanical-connection to vibrate in accordance with signals desired to modulate high frequency oscillations, said means comprisinga piezo-electric crystal device arranged to vibrate mechanically in response to electrical oscillations corresponding to signals desired to modulate said high frequency oscillations.

7 In a system for producing electrical oscillations of relatively high frequency, mod- "ulated at a range of relatively lower frequencies, a thermionic amplifier, input and output circuits connected therewith, a plurality of piezo-electric crystal devices, one of said crystal devices being connected in said input circuit,'another of said crystal devices being connected in said output circuit, a mechanical connection formed by a link of piezoelectrically inactive material extending between said crystal devices, said mechanical connection being so chosen and arranged that the natural frequency of the system corresponds to the frequency of oscillations desired, and means for causing said mechanical connection to vibrate in accordance with signals desired to modulate high frequency .oscillations, said means comprising a piezoelectric crystal device arranged to vibrate,

mechanically in ,responseto electrical oscillations corresponding'to signals desired to modulate said high frequency oscillations,

and means for impressing thereon'such oscillations.

, 8. In a system for producing electrical oscillations of relatively high frequency,modulated at a range of relatively lower frequencies, a thermionic amplifier, input and output circuits connected therewith, a plurality of piezoelectric crystal devices, one of said crystal devices being connected in said input circuit, another ofsaid crystal devices being connected in said output circuit, a mea clianical connection formed by a link of piezoelectrically inactive material extending between said crystal devices, said mechanical connection being so chosen andarranged that the natural frequency of the system corresponds to'the frequency of oscillations desired, and means for causing said mechanical connection to vibrate inaccordance withsignals desired to modulate high'fre'quency 0scillations, said means comprising a piezoelectric crystal device arranged to vibrate mechanically in response to electrical-oscillations corresponding to signals desired to modulate said high frequency oscillations, and means for impressingthereonsuch oscillations, such means comprising a piezo-electric crystal device arranged to convert acoustic signals into electrical oscillations corrc sponding thereto.

9. A pieZo electric modulator-oscillator comprising, two piezo electric devices having widely different frequency characteristics, means associated with one of said piezo electric devices for sustaining high frequency mechanical vibrations therein, means for impressing relatively low frequency vibrations upon the other of said piezo electric devices, and mechanical coupling means connecting said piezo electric devices whereby the high frequency mechanical vibrations of the first mentioned piezo electric device are transmitted to the seond mentioned piezo electric device and are modulated with said low frequency vibrations.

10. A system for producing high frequency electrical oscillations modulated with a band of low frequency electrical oscillations, comprising, an electron discharge device having an input circuit and an output circuit associated therewith and adapted to generate high frequency electrical oscillations, a piezo electric device associated with said 7 output circuit and adapted to convert said electrical oscillations into mechanical vibrations, a second piezo electric device associated with said input circuit and adapted to vibrate in accordance with acoustical vibrations, said second piezo electric device having widely diflerent electrical and mechanical characteristics from said first piezo electric device, and mechanical coupling means connecting the said piezo electric devices and adapted to transmit said mechanical vibrai; tions from the first mentioned piezo electric device to the second mentioned piezo electric device, whereby electrical oscillations corresponding to said mechanical vibrations are modulated with electrical oscillations corresponding to said acoustical vibrations.

In testimony whereof I hereunto affix my signature. I ALEXANDER MoLEAN NICOLSON. 

